Aromatherapy is the practice of using essential oils extracted from plants to enhance psychological and physical well-being through topical application or inhalation. New studies show that humans can distinguish at least 1 trillion scents.

The 5 most popular oils currently in use are lavender, peppermint, tea tree, eucalyptus, and rosemary.

The human body contains far more receptors for smell (at least 1,000) than it does for other senses, such as sight (four) and touch (at least four).

Essential oils are extremely concentrated. More than 5 undiluted drops should never be applied directly on the skin unless directed.

Aromatherapists do not advise mixing more than 5 scents at a time.

The shelf life for most essential oils is about 12 months.

The highest-quality essential oils come from steam distillation or cold pressing plant and flower parts.

Hydrosols are the aqueous byproducts of the distillation process (like rosewater) and have culinary, medicinal, and skin care uses.

Essential oils should never be ingested.

Essential oils can be extracted from the bark, stems, leaves, roots, and petals of herbs or flowers.

Fragrance oils are chemical mixtures that mimic natural plant aromas and are not appropriate for aromatherapy.

Aromatherapy works by stimulating the nervous and limbic system, the parts of the brain that affect emotion and memory.

Aromatherapy scents can be applied through topical skin care, massage, baths, air diffusers, or direct inhalation.